Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual Social e Democratas Liberais/ Democratas Liberais têm um Controle de trabalho mantido, e um Liberal maior que 0?
 ###Tabelas: CREATE TABLE summary_of_election_results_1973_-_2003 (summary_of_election_results_1973_-_2003_id AUTO_INCREMENT PRIMARY KEY, Election INT, Labour INT, Conservative INT, Liberal INT, Social Democratic Party INT, Social and Liberal Democrats/ Liberal Democrats INT, Independent INT, Green INT, Other VARCHAR, Control VARCHAR) CREATE TABLE singles:_17_10–7 (singles:_17_10–7_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Date VARCHAR, Tournament VARCHAR, Surface VARCHAR, Opponent VARCHAR, Score VARCHAR) CREATE TABLE contemporary_humor_magazines (contemporary_humor_magazines_id AUTO_INCREMENT PRIMARY KEY, Title VARCHAR, Language VARCHAR, Country VARCHAR, Years published VARCHAR, Frequency VARCHAR, Medium VARCHAR, Classification VARCHAR) CREATE TABLE most_wickets (most_wickets_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, Matches VARCHAR, Overs VARCHAR, Wickets VARCHAR, Economy Rate VARCHAR, Average VARCHAR, Strike Rate VARCHAR) CREATE TABLE table_of_the_most_commonly_used_of_the_traditional_essential_dignities (table_of_the_most_commonly_used_of_the_traditional_essential_dignities_id AUTO_INCREMENT PRIMARY KEY, Sign VARCHAR, Domicile VARCHAR, Detriment VARCHAR, Exaltation VARCHAR, Fall VARCHAR)  
SELECT SUM Social and Liberal Democrats/ Liberal Democrats FROM summary_of_election_results_1973_-_2003 WHERE Control = labour hold AND Liberal > 0